Variable output pump control circuit using a remote control

ABSTRACT

A variable output pump control circuit using a remote control valve for switching two control valves which control the operation of hydraulic actuators and control the switching of the servo motor of a variable output pump by means of pilot pressure from the remote control valve. A control circuit is provided in the pilot circuit of the variable output pump for controlling switching by means of the pilot pressure from the remote control valve. Thus, insufficient hydraulic pressure in the pilot circuit, which occurs when the flow rate in the remote control valve is small, is eliminated.

United States Patent 1 [111 3,871,178 Tominaga Mar. 18, 1975 VARIABLEOUTPUT PUMP CONTROL 3,486,334 12/1969 Miller 60/445 x CIRCUIT USING AREMOTE CONTROL 3,672,I6l 6/l972 Krusche et al 60/445 X HiroyoshiTominaga, Osaka, Japan Kabushiki Kaisha Komatsu Seisakusho, Tokyo, JapanFiled: Sept. 6, 1973 Appl. N6; 394,664

Inventor:

Assignee:

Foreign Application Priority Data Oct. SI, 1972 Japan 47-108463References Cited UNITED STATES PATENTS 6/1960 Carlson et a] 60/433 XPrimary Examiner-Edgar W. Geoghegan Attorney, Agent, or FirmArmstrong,Nikaido & Wegner [57] ABSTRACT A variable output pump control circuitusing a remote control valve for switching two control valves whichcontrol the operation of hydraulic actuators and control the switchingof the servo motor of a variable output pump by means of pilot pressurefrom the remote control valve. A control circuit is provided in thepilot circuit of the variable output pump for controlling switching bymeans of the pilot pressure from the remote control valve. Thus,insufficient hydraulic pressure in the pilot circuit, which occurs whenthe flow rate in the remote control valve is small, is eliminated.

2 Claims, 2 Drawing Figures PATEHTEU 1 8 I975 SHEET 1 [If 2 VARIABLEOUTPUT PUMP CONTROL CIRCUIT USING A REMOTE CONTROL BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to ahydraulic circuit of a hydraulic power shovel, and more particularly toa variable output pump control circuit using a remote control valve forcontrolling the control valve and the variable output pump of thehydraulic power shovel.

2. Prior Art Conventional variable output pump control circuits for thehydraulic circuit of a hydraulic power shovel have a pilot pump, twocontrol valves for controlling the operation of two actuators for thepower shovel, a variable output pump with a servo motor, and a remotecontrol valve having four control valves connected at the secondaryports thereof to the pilot ports of the two control valves. The twocontrol valves each have two opposite springs for urging spools at bothsides thereof. This control circuit also has a throttle valve in thedrain circuit of the pilot circuit of the variable output pump.

In a variable output pump control circuit as described above, when theremote control valve receives hydraulic oil from the pilot pump, itblocks the pilot pressure with a handle positioned in neutral. If one ofthe control valves of the remote control valve is operated, thesecondary output pressure thereof is linearly varied from zero to apredetermined pressure responsive to the stroke of the spool thereof orto the inclining angle of the manually operated lever. When the otherthree control valves of the remote control valve are operated, a similaroperation is performed. Then, when the hydraulic pressure is changedfrom zero to a predetermined pressure by the remote control valve thepressure is applied to the spools of the two control valves, the spoolsof the control valves are varied linearly in such a manner that thehydraulic pressures applied thereto and the tensions of the springs arebalanced. However, when the servo motor of the variable output pump isalso controlled by the pilot pressure from the remote control valve, thedischarge amount of the pump is varied linearly with respect to thestroke of the spool of the remote control valve. Further, after thehydraulic pressure from the remote control valve operates the servomotor of the variable output pump, the throttle valve provided in thedrain circuit of the pilot circuit of the variable output pumpneutralizes the remote control valve and returns the servo motor to itsinitial state by allowing the hydraulic fluid in the pilot circuit toescape while the passage to the remote control valve is blocked by acheck valve.

However, the conventional variable output pump control circuit which hasthe throttle valve in the drain circuit of the pilot circuit has thefollowing disadvantages: (1) When the hydraulic flow rate from theremote control valve is small such as when the engine speed is low, theleaking rate of the hydraulic oil from the throttle valve becomes largethus the hydraulic pressure in the pilot circuit becomes insufficient.(2) If the throttle valve is excessively throttled in order to avoid theabove situation, the returning of the servo motor of the variable outputpump is slow with the result that the returning of the inclined plateangle of the pump to neutral position becomes slow, thus theresponsiveness of the system is slow.

SUMMARY OF THE INVENTION It is, therefore, an object of the presentinvention to provide a variable output pump control circuit using'aremote control valve which may normally operate the servo motor thereofeven if the engine speed is low.

It is another object of the present invention to provide a variableoutput pump control circuit using a remote control valve which mayquickly return the servo motor to its initial state, thus greatlyimproving the re sponsiveness thereof.

It is a further object of the present invention to provide a variableoutput pump control circuit using a remote control valve which mayfreely adjust the returning speed of the servo motor.

In order to perform the aforementioned and other objects of the presentinvention, there is provided a variable output pump control circuitusing a remote control valve for switching two control valves whichcontrol the operation of hydraulic actuators and also which switch theservo motor of the variable output pump by means of pilot pressure fromthe remote control valve. A control circuit is provided in the pilotcircuit of the variable output pump for switching, by means of the pilotpressure from the remote control valve, so that the total flow from thepilot circuit is to the servo motor when controlling the servo motor ofthe variable output pump and all the hydraulic oil is drained from theservo motor when returning the servo motor to its initial state. Thiseliminates the disadvantages of the conventional variable output pumpcontrol circuit.

DETAILED DESCRIPTION OF THE DRAWINGS These and other objects, featuresand advantages of the present invention will become more fully apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a hydraulic control circuit of a conventional variable outputpump control circuit using a remote control valve; and

FIG. 2 is a hydraulic control circuit of a variable output pump controlcircuit according to the present invention.

PREFERRED EMBODIMENTS For better understanding of the present invention,the conventional variable output pump control circuit willnow bedescribed with reference to FIG. 1, which shows a hydraulic circuit of aconventional variable output pump control circuit.

The conventional variable output pump control circuit has, as in FIG. 1,a pilot pump 2, two control valves 7 and 8 for controlling the operationof two actuators for a power shovel. The circuit also includes avariable output pump 10 with a servo motor 11, and a remote controlvalve 1 having four control valves 10, lb and 1c, 1d connected at thesecondary ports thereof to the pilot ports of the two control valves 7and 8, respectively. The two control valves 7 and 8 each have twoopposite springs 9 for urging the spool thereof at both sides. Thecontrol circuit also has a throttle valve 13 in the drain circuit of thepilot circuit 12 of the variable output pump 10.

In this variable output pump control circuit, when the remote controlvalve 1 receives hydraulic oil from the pilot pump 2, it blocks thepilot pressure with a handle (not shown) manually positioned in neutral.If one of the control valves 1a, 1b, 1c and 1d of the remote controlvalve 1 is operated, the secondary output pressure thereof is variedlinearly from zero to a predetermined pressure P responsive to thestroke of the spool thereof or to the inclining angle of the manuallyoperated lever (not shown). If the other three control valves of theremote control valve 1 are operated, a similar operation is performed.The hydraulic pressure from the remote control valve 1 is applied to thespools of the two control valves 7 and'8, and the spools of the controlvalves 7 and 8 are varied linearly in such a manner that the hydraulicpressures applied thereto and the tensions of the springs 9 arebalanced. The servo motor 11 of the variable output pump 10 is alsocontrolled by the pilot pressure from the remote control valve 1, thedischarge amount of the pump 10 is also varied linearly with respect tothe stroke of the spool of the remote control valve 1. Further, afterthe hydraulic pressure from the remote control valve 1 operates theservo motor 11 of the variable output pump 10, the throttle valve 13,provided in the drain circuit of the pilot circuit 12 of the variableoutput pump 10, neutralizes the remote control valve 1 to return theservo motor 11 to its initial state by permitting the escape of thehydraulic fluid in the pilot circuit 12 when the passage to the remotecontrol valve 1 is blocked by a check valve (not shown).

Referring now to FIG. 2, which shows a hydraulic circuit of oneembodiment of a variable output pump control circuit using a remotecontrol valve constructed according to the present invention, whereinthe like numerals correspond to those shown in FIG. 1, the variableoutput pump control circuit of this invention comprises a controlcircuit 15 provided in the pilot circuit 12 for supplying the pilotpressure to the servo motor 11 of the variable output pump 10 from theremote control valve 1. The control circuit 15 includes a valve 16having a communication position or section 16a for connecting the pilotcircuit 12 with the servo motor 11 and a drain position or section 16bfor blocking the pilot circuit 12 and also for connecting the returnfluid or oil of the servo motor 11 to the drain circuit. The circuitalso includes a spring 18 coupled to a control valve 16 disposed at oneend of the spool thereof to urge the spool for connecting the section16b with the drain circuit l7, and a control passage 19 forautomatically switching the state of the control valve. The controlpassage 19 connects the pilot circuit 12 between the control valve 16and the remote control valve 1 to the drain circuit 17. A pilot passage20 is provided in the control passage 19. The passage 20 is connected toside end surface of the section 16a of the control valve 16, and athrottle valve 21 is provided at the drain circuit 17 side of the pilotpassage 20.

In FIG. 2, numerals 22 and 23 represent hydraulic actuators.

In the variable output pump control circuit thus constructed, when theremote control valve 1 is operated so as to supply hydraulic fluid oroil to the pilot circuit 12, the hydraulic fluid flows to the controlpassage 19, and is throttled by the throttle valve 21 thus increasingthe pilot pressure in the pilot passage 20. Thus, the control valve 16normally urged by the spring 18 to the position shown in FlG. 2 isswitched so that the section l6a is connected to the pilot circuit 12with the result that all the fluid or oil from the remote control valve1 flows into the servo motor 11 of the variable output pump 10 tooperate the variable output pump 10.

When the remote control valve 1 is operated to shut off the supply ofhydraulic fluid to the pilot circuit 12, the pilot pressure in thecontrol passage 19 is released so that the control valve 16 is returnedby the spring 18 with the result that the servo motor 11 is drained viasection 16b through the drain circuit 17.

It should be understood from the foregoing description that the variableoutput pump control circuit uses a remote control valve 1 for switchingtwo control valves 7 and 8 for controlling the operation of hydraulicactuators 22 and 23 and also for switching the servo motor 11 of avariable output pump 10. The circuit comprises a control circuit 15 inthe pilot circuit 12 of the variable output pump 10 for connecting theremote control valve 1 with the servo motor 11 of the variable outputpump 10. The control circuit has a control valve 16 having a section 16afor connecting the pilot circuit 12 to the the servo motor 11 and asection 16b for blocking the pilot circuit 12 and also for connectingthe return fluid of the servo motor 11 with the drain circuit. A. spring18 is so disposed at one end of the spool of valve 16 to urge the spoolfor connecting the section 16b with the drain circuit 17. A controlpassage 19 is connected to the pilot circuit 12 and has a throttle valve21 provided at the drain circuit side of the pilot passage forthrottling pressure at the other end of the control valve 16. The pilotpressure which operates the servo motor 11 of the variable output pump10 is derived from all the hydraulic fluid supplied from the remotecontrol valve 1. Thus even if the engine is at low speed, the servomotor 11 will operate normally. Particularly, even if the fluid flowrate is very low due to throttling of the throttle valve 21, no troubleis caused.

It should also be understood that when the servo motor 11 is returned tothe neutral position, the hydraulic fluid of the servo motor 11 isdrained to the drain circuit 17 without resistance with the result thatthe returning of the servo motor 11 is rapid so as to greatly improveits responsiveness.

It should also be understood that if the throttle valve 21 is soprovided as to be adjustable, the returning speed of the servo motor 11may be freely adjusted.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresently disclosed embodiments are therefore to be considered in allrespects as illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims rather than the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

l. A variable output pump control circuit using a remote control valvefor switching two control valves which control the operation ofhydraulic actuators and also for switching a servo motor of a variableoutput pump, comprising control circuit means in a pilot circuit of saidvariable output pump for connecting said remote control valve with saidservo motor, said control circuit means including: switching a controlvalve, having a first section for connecting the pilot circuit with saidservo motor, a second section for blocking the pilot circuit and forconnecting said servo motor with a drain circuit, and a spring meansdisposed at one end other end of the switching control valve.

2. A variable output pump control circuit according to clairn 1, whereinsaid throttle valve is adjustable.

1. A variable output pump control circuit using a remote control valvefor switching two control valves which control the operation ofhydraulic actuators and also for switching a servo motor of a variableoutput pump, comprising control circuit means in a pilot circuit of saidvariable output pump for connecting said remote control valve with saidservo motor, said control circuit means including: switching a controlvalve, having a first section for connecting the pilot circuit with saidservo motor, a second section for blocking the pilot circuit and forconnecting said servo motor with a drain circuit, and a spring meansdisposed at one end of the spool of the switching control valve to urgethe spool to connect said second section with said drain circuit; acontrol passage means connected to said pilot circuit; and a throttlevalve at the drain circuit side of the control passage for throttlingflow to or from the other end of the switching control valve.
 2. Avariable output pump control circuit according to claim 1, wherein saidthrottle valve is adjustable.